boards: add new test supported feature usbd

We have recently added a new platform where the USB controller is only
supported in the new USB device support. This forces us to introduce a
new supported feature tag to distinguish the dependency. Use "usbd",
which is also the prefix of the new device support.

There are many boards that already have new driver support, but we will
replace the "usb_device" feature when the old device support is
deprecated.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>